Various glycoproteins (hereinafter to be referred to as GP) are present on the surface of a platelet membrane, and are involved in the expression of platelet functions. Of such platelet membrane glycoproteins, GPIb, GPIIb, GPIIIa, GPIIIb, GPIV, GPIX and the like are known. Of these, GPIb functions as a receptor of the von Willebrand Factor (hereinafter to be referred to as vWF). GPIb is a heterodimer having a molecular weight of 160,000, wherein α chain and β chain are bonded via a disulfide bond (Proc. Natl. Acad. Sci. USA, Vol. 84, pp. 5615-5619, 1987, Hematology & Oncology, Vol. 31, No. 1, pp. 5-10, 1995 and the like).
When vascular damages are caused, platelets quickly adhere to the vascular lesion and form a platelet thrombus by aggregation and the like. In forming the platelet thrombus, vWF plays an important role as an adhesive protein. It is considered that GPIb binds with vWF as its receptor and activates or promotes adhesion and aggregation of platelets via vWF at said vascular lesion. In addition, the binding of vWF and GPIb functions to stop bleeding at the vascular lesion but also forms a pathologic thrombus. Thus, effective use of GPIb for the examination and diagnosis of vascular lesion, detection of pathologic thrombus, and treatment thereof is expected.
Nevertheless, the use of isolated GPIb has not proved successful in artificial expression of the physiological activity as mentioned above. In other words, some idea in the aspect of formulation of pharmaceutical preparations is needed to practically use GPIb as a pharmaceutical agent or reagent.
The present inventors first found earlier that the physiological activity of GPIb could be expressed by preparing a lipid complex containing a conjugate of GPIb and a particular lipid, and a general lipid (WO97/29128, JP-A-9-208599, U.S. Pat. No. 6,177,059, EP-894807-A).